The present invention relates to a temperature-difference-actuated pump, particularly, to such a pump operating from a low-level heat source such as solar heat or an effluent from an industrial plant or the like. Such pumps are particularly well suited for use in developing countries, especially in agricultural uses such as for pumping irrigating water, where other energy sources may not be readily available. Yet more specifically, the invention relates to such a pump which requires the use of no electrical valves, making it particularly useful in such applications.
The present applicant has proposed such a pump for converting the energy of low-level sources such as mentioned above into potential energy in the form of raised water supply. (See Kagaku Kogaku Ronbunshu (Japan), Vol. 9, No. 6, pp. 698-700, Nov. 1983). Such a pump is shown schematically in FIG. 1.
In FIG. 1, reference character A identifies a boiler; B, a condenser; C, a pumping chamber of constant volume; D, an inflatable bag provided inside the chamber C; E, F and I, electrically operated solenoid valves; G and H, non-return valves; X, a supply tank; and Y, a receiving tank.
This pump operates as follows: An working fluid, which may be a common refrigerant such as FREON, then contained in the boiler A is therein heated by the low-level heating source to cause it to evaporate. Suppose the pressure of the chamber C (space around the bag D) is as low as that of the condenser B, and the bag D is filled with water. The valve F is opened and the remaining valves closed. Vaper of the working fluid passes through the valve F and goes into the space in the chamber C around the bag D. The bag D is squeezed and the water in the bag D is lifted to the receiving tank Y through the non-return valve H. The valve F is then closed and the valve I opened. The working fluid then is condensed in the condenser B, lowering the pressure in the chamber C and thus causing the bag D to expand, sucking in water from the supply tank X through the non-return valve G. The valve I is closed and the valve F is opened again so that the water filled bag D is squeezed and the water is again lifted to the receiving tank Y. This water-lift cycle is repeated with a considerable amount of condensed working fluid accumulated in the condenser B. The valve E is then opened to permit the condensed liquid to flow into the boiler A. The valve F is then opened again and the process repeated.
A modification of the pump of FIG. 1 is shown in FIG. 2. In this modification, the outlet of the bag D is communicated through a pipe J to a closed tank K. The tank K provided with a non-return valve L is immersed in the supply tank X and connected to the receiving tank Y through a pipe N and a non-return valve M. This pump operates substantially in the same manner as that depicted in FIG. 1 except that air is used as a working medium in the bag D. Using the same cycle explained above, the air expelled from and sucked into the bag D performs a pumping action by expelling water from and sucking water into the closed tank K.
In both the pumps of FIGS. 1 and 2, electrically operated solenoid valves are required. In some areas of developing countries, for instance, electricity is not readily available, and in such situations, these pumps are useless.